In IC manufacturing methods, thin films are formed on wafers by the depressurizing CVD (chemical vapor deposition) method.
In recent years, in order to resolve problems when loading the wafer into the reaction furnace such as semiconductor deterioration due to impurities adhering to the semiconductor or an increase in the natural oxidation film, a method is utilized where a prechamber is installed at a stage prior to the reaction furnace; and oxygen and moisture are removed in sufficient amounts from the prechamber, and after replacing the prechamber atmosphere with nitrogen gas, the wafers are loaded into the reaction furnace.
A vertical type depressurizing CVD apparatus with reaction furnace prechamber (hereafter called, CVD apparatus with prechamber) is widely utilized to implement the depressurizing CVD method.
In this CVD apparatus with prechamber, a prechamber with a sealed structure that allows drawing a vacuum is installed at a stage prior to the reaction furnace.
Prior to processing, the wafers are loaded into the prechamber from a wafer loading/unloading opening and set in a boat serving as the wafer processing jig. The prechamber is then sealed in an airtight state, and oxygen and moisture removed by drawing a vacuum and purging with nitrogen gas repeatedly. The wafers are then loaded from the prechamber into the reaction furnace by the boat (boat loading).
However, a drive shaft unit and boat rotator mechanism and a wiring unit are installed within the prechamber in the CVD apparatus with prechamber to load the wafers and the boat into the reaction furnace. These components might possibly contaminate the wafer surface with impurities such as organic substances while drawing a vacuum.
A hydrogen (H2) annealing method was utilized in the reaction furnace where the wafers are loaded, as a technique using reactive gas to remove impurities or the natural oxidation film on the wafer.
An example of this technology is disclosed in the patent document 1.
Patent document 1: Japanese Patent Non-examined Publication No. 5-29309